Measure watch stats in robustness tests like traffic stats

[serathius]

What would you like to be added?

Like for KV values:

etcd/tests/robustness/traffic/traffic.go

Lines 159 to 189 in 05b8563

	func CalculateStats(reports []report.ClientReport, start, end time.Duration) (ts trafficStats) {
	ts.Period = end - start
	for _, r := range reports {
	for _, op := range r.KeyValue {
	if op.Call < start.Nanoseconds() || op.Call > end.Nanoseconds() {
	continue
	}
	resp := op.Output.(model.MaybeEtcdResponse)
	if resp.Error == "" {
	ts.Successes++
	} else {
	ts.Failures++
	}
	}
	}
	return ts
	}
	type trafficStats struct {
	Successes, Failures int
	Period time.Duration
	}
	func (ts *trafficStats) SuccessRate() float64 {
	return float64(ts.Successes) / float64(ts.Successes+ts.Failures)
	}
	func (ts *trafficStats) QPS() float64 {
	return float64(ts.Successes) / ts.Period.Seconds()
	}

Expect this is a separate structure. No need to measure values against failpoint injection like we do for KV.

Measure for watch:

• Number of watch requests
• Number of events collected
• Number of progress notifies
• Number of watch requests that were immediately closed
• Coverage of revisions
• Average duration of watch

Maybe propose some validation based on metrics

/cc @nwnt @joshjms

Why is this needed?

Have some quality quantifier for watch like we have for KV operations.

[rockswe]

/assign